Ambush alley

THE THUD OF KILLER WHALE SNOUT smashing gray whale blubber lingers over an otherwise tranquil ocean. It’s unnerving, says researcher Nancy Black, to sit a few feet away in an inflatable boat, watching and listening as a gray whale calf absorbs blow after blow to its tender belly while clinging to a mother that struggles to defend it.

It’s also satisfying.

As gray whales reach Monterey Bay on their migration from Baja California to the Bering Sea each spring, they have two choices: follow the meandering coast or chance the more direct route across the outer bay’s expansive submarine canyon. The shortcut is where killer whales lie in ambush and where Black, too, lies in wait.

Days after witnessing that assault on the calf, the season’s first recorded attack, Black is back observing marine life while lecturing paying passengers over a PA system. This is her real job: naturalist aboard the Sea Wolf II, her primary whale-watch vessel. Whichever boat she’s on, though, her main focus is on the killer whales.

As Sea Wolf plods west into a brisk morning wind, she scours the horizon through beat-up binoculars. Assistant Sarah Graham is with her. So is Alisa Schulman-Janiger, director of the American Cetacean Society’s gray whale census project in Los Angeles and Black’s partner in a project to use photographs to identify killer whales -- part of the only year-round study of transient killer whales along the West Coast.

Researchers estimate that killer whales cull less than 2% of the migrating gray whale calves in a season. This doesn’t threaten the overall gray whale population, which numbers about 20,000. The project is for the sake of better understanding an animal about which little is known. (Scientists don’t refer to the species Orcinus orca as orcas; it would be like calling humans just sapiens, they say.)

So far, researchers have cataloged nearly 350 killer whales, using distinct markings on their dorsal fins or the unique shape and coloration of their saddle areas. A network of scientists and captains, from Mexico to Alaska, keeps Black and her team supplied with sighting information they hope will shed more light on the mammals’ movements and behavior. “The long-term goal,” Schulman-Janiger says, “is to identify all the killer whales in California and to document their life histories through our tracking program.” Researchers are also collecting biopsy samples to determine the extent of contaminants in their bodies -- they’ve been found to be very high in some types -- and learn more about genetic relationships.

Scientists have classified three distinct types of killer whales that prowl California waters.

The offshore pod, so named because it tends to disappear for long periods, presumably well offshore, travels in large groups and feeds mainly on fish.

The L.A. pod, a much smaller group of much smaller killer whales (adults barely reaching 20 feet, as opposed to nearly 30 feet for others), was spotted frequently off the Palos Verdes Peninsula from 1982 to 1990, then mysteriously disappeared from 1991 to 1995. The last known sighting was of three adults off La Jolla in 1997, and researchers are concerned that this pod may no longer exist.

Finally there are the transients, the only full-fledged mammal eaters, which appear sporadically throughout the year off Monterey and have been seen terrorizing everything from birds to whales.

As the Sea Wolf II rises and dips over the wind-driven swell, flushing all color but green from the faces of some passengers, research assistant Peggy Stap passes around photos of an attack last October on a Pacific white-sided dolphin. A group of transients separated the dolphin from its pod, chased it close to the boat, came up beneath it and flipped it skyward several times, eventually consuming the creature as horrified whale watchers looked on.

One of the attackers was CA 39, a killer whale that had previously appeared on the BBC’s popular “Blue Planet” documentary, tearing into a freshly killed gray whale calf. An adult female, CA 39 has been spotted more than 50 times since researchers first documented her here in 1991. Black knows her from a distance.

CA 51 was also in on that slaughter. She’s a dominant member of what Black calls “the friendly pod” because it has made so many close approaches. She’s often seen with CA 50. They might be sisters, and both are accompanied by juvenile offspring. CA 50 is believed to be the mother of CA 53, or Starfin, an older juvenile with very unusual markings on its dorsal fin -- and one that has learned well the fine art of whale killing.

Black and her team have photo-cataloged 145 transient individuals. Their informal spotting team has photographed them as far north as Alaska and as far south as Santa Catalina Island. At recent marine mammal conferences in North Carolina and France, they told audiences that their videotapes of attacks show that killer whales most often eat sea lions, followed by gray whale calves, Dall’s porpoises, elephant seals, harbor seals, seabirds and miscellaneous dolphin species.

Adult females with calves and male pairs did most of the killing of gray whales. The females often prolonged the attacks up to six hours, leading the scientists to believe the mothers were instructing their young.

During the assaults, each killer whale performed a task. Some, for instance, worked to keep the gray whale mother away from her calf. Another rammed the calf and still another held it down in an attempt to drown it. During one attack, CA 39 and CA 50 took turns doing the separating, a role whose risk is probably evidenced, researchers say, by the deep gash on CA 50’s dorsal fin.

Black and her team know many of the killer whales individually. They know when and where they were last seen. Black has watched some grow up and others grow old and drop out of the picture. She finds their behavior infinitely fascinating.

In hopes of avoiding detection, for instance, gray whales will “snorkel” as they cross the canyon, staying near the surface and taking smaller, quieter breaths. If ambushed, they’ll run for shallow water. If surrounded, the mother will use her fluke to slap ferociously at her attackers, or roll over and allow the calf onto her belly.

After each slaughter the killer whales call in others to join a feast that can last more than 10 hours. Black recalls the time in 1998 when the whales abruptly left one kill to swim to another nearly 10 miles away. “There definitely had been some kind of vocalization,” Schulman-Janiger says.

Being a scientist, Black is reluctant to acknowledge a personal bond with the animals. “But they might recognize us,” she confesses quietly, as if violating a professional code. “They seem almost as curious about us as we are about them. We think they might be seeking interaction.”

Before the attack on the calf off Carmel, for example, the same five killer whales, led by CA 51, milled around the 22-foot inflatable for 15 minutes. Graham reached down and almost touched one as it hovered vertically just beneath the surface, peering upward. Capt. Andy, the scientist’s black Lab, tossed them a Frisbee. They ignored it.

Two weeks later, Black watched from the inflatable as CA 51, along with a calf, a juvenile and a young adult known as CA 27, corralled a school of salmon.

That was unusual. But not as unusual as what followed.

The juvenile surfaced with a dead salmon in its teeth and gently released it alongside the inflatable. A crew member reached out and hauled it aboard, earmarked for dinner.

“It makes you wonder,” Black says.